"You want to do a hard reset of the phone to the factory settings that wipes the phone completely so any personal data is off your connection with the itunes account that's cleared, photos, apps, all of that. Just make sure you back up your device first," says Ken German.

And, if you want to hold on to your precious unlimited plan, resist the urge to preorder online.

You'll have better luck getting that plan grandfathered-in by talking to someone with your service provider in person.